Platelet aggregation examination has been known as a test for evaluating platelet function. In a platelet aggregation examination, platelets are caused to aggregate by adding an activator to the platelets to induce the platelets to aggregate, and platelet aggregation is evaluated by monitoring the change in the level aggregation over the course of the platelet aggregation reaction. Platelet aggregation is also known to be promoted by shearing stress on the platelets in the blood stream. Methods which measure platelet aggregation by mixing a measurement sample in order to promote platelet aggregation by adding a shearing stress on the platelets are known (for example, refer to U.S. Pat. No. 6,773,923).
U.S. Pat. No. 6,773,923 discloses a method of measuring platelet aggregation in which a first reaction phase is conducted during which a measurement sample that has been prepared from a sample and reagent is reacted by mixing at a predetermined speed, and thereafter platelet aggregation is measured during a second reaction phase during which the measurement sample is mixed at a speed that is lower than the predetermined speed, or not mixed at all.
The measurement sample is generally prepared by dispensing a sample and a reagent into a predetermined container. The prepared measurement sample is in a state in which the sample and reagent are not uniformly mixed in the measurement sample until the measurement sample is subjected to agitation. Although not clearly stated in U.S. Pat. No. 6,773,923, it is believed that measurement samples are in a state in which the sample and reagent are not uniformly mixed when the measurement sample is subjected to mixing in the first reaction phase in U.S. Pat. No. 6,773,923.
When a reaction (aggregation) is produced by mixing a sample and a reagent of a measurement sample in a state in which the sample and reagent are not uniformly mixed, localized reactions disadvantageously begin between the sample and the reagent when mixing starts. Since the extent of the reaction (aggregation) caused by such localized reactions differs depending on the conditions under which the sample and the reagent are mixed, fluctuations of the measurement results are produced due to the change over time in the aggregation reaction. The problem of unstable measurement results therefore occurs with such measurement methods.